Scratch board and method of manufacturing and using same

ABSTRACT

The present invention is a scratch board for laying on a sub-floor to form a foundation for floor tiles. The scratch board consists of a rectangular flat board made of cement and has opposite first and second surfaces. The board has a metal screen extending throughout the board parallel between the first and second surfaces and a mesh screen extending throughout the board and imbedded in the first surface. The scratch board is used to construct a tile floor by first covering the sub-floor with a plurality of the boards and securing them to the sub-floor with a staples. A tile adhesive is then spread overtop of the boards and the tiles are then laid onto the adhesive. The boards themselves are manufactured by first placing the mesh screen and then the metal screen into a rectangular form. Wet cement is then poured into the rectangular form and then leveled to form one of the surfaces. The cement is left to cure before removing the finished board from the form.

FIELD OF THE INVENTION

The invention relates generally to methods and compositions for laying floor tiles.

BACKGROUND OF THE INVENTION

Laying floor tiles is a time consuming process involving numerous labor intensive steps. Firstly, a metal screen has to be laid over top of the sub floor and stapled in place. This requires cutting the screen into sections and laying the sections in end to end alignment on the sub-floor. The screens are then stapled to the sub-floor to hold them in place. After the screen is laid on the sub-floor, cement is mixed and then layered onto the metal screen. This requires the mixing of the cement mixture, the troweling of the cement into and onto the metal screen, the leveling of the cement and then the hardening and curing of the cement. In addition to being a dirty and time consuming process, the troweling of the cement requires the use of a cement mixing device. Furthermore, the hardening and curing process can take anything from one to several days depending on the relative humidity and the temperature. The floor cannot be walked on during the hardening/curing process, making it more difficult to apply the cement. Finally, after the cement if fully cured, a layer of tile adhesive can be applied to the top surface of the cement and the tiles applied.

The laying of the cement layer is required since tiles cannot be applied directly to the sub-floor. The laying of the cement is often the rate limiting step requiring the most amount of labor and time. Therefore, a system which stream lines the laying of the cement over the sub-floor would increase the productivity of the process.

SUMMARY OF THE INVENTION

In accordance with the present invention, there is provided a scratch board for laying on a sub-floor to form a foundation for floor tiles. The scratch board consists of a rectangular flat board made of cement and having opposite first and second surfaces. The board has a metal screen extending throughout the board parallel between the first and second surfaces and a mesh screen extending throughout the board and imbedded in the first surface.

The invention also includes a method of manufacturing a tile floor using the scratch boards mentioned above consisting of the steps of covering the sub-floor with a plurality of boards and securing the boards to the sub-floor with a plurality of staples. A tile adhesive is then spread overtop of the boards after the boards have been secured to the sub-floor and then the tiles are laid onto the adhesive.

The invention further includes a method of manufacturing the scratch board described above consisting of placing the mesh screen into a rectangular form and then placing the screen over top of the mesh screen in the rectangular form. Wet cement is then poured into the rectangular form containing the mesh screen and metal screen. The cement in the form is then leveled to form one of the surfaces and the cement is left to cure before removing the finished board from the form.

With the foregoing in view, and other advantages as will become apparent to those skilled in the art to which this invention relates as this specification proceeds, the invention is herein described by reference to the accompanying drawings forming a part hereof, which includes a description of the preferred typical embodiment of the principles of the present invention.

DESCRIPTION OF THE DRAWINGS

FIG. 1. is a top view of a scratch board made in accordance with the present invention showing the different layers of the scratch board.

FIG. 2. is a cross-sectional view of the scratch board showed in FIG. 1.

FIG. 3. is a schematic view of the first steps in the process of manufacturing of the scratch board of the present invention.

FIG. 4 is a schematic view of the process of manufacturing of the scratch board of the present invention.

FIG. 5 is a top view a floor made using the scratch board of the present invention.

FIG. 6 is a cross sectional view of the floor illustrated in FIG. 5.

In the drawings like characters of reference indicate corresponding parts in the different figures.

DETAILED DESCRIPTION OF THE INVENTION

Referring firstly to FIGS. 1 and 2, a scratch board made in accordance with the present invention is shown generally as item 10 and consists of a rectangular board 12 having opposite surfaces 14 and 16. Board 12 is made of cement and has fabric mesh screen 18 embedded in surface 16 and metal screen 20 embedded in cement 22. Metal screen 20 comprises a standard expanded galvanized steel screen as used to form concrete floors and the like. Metal screen 20 is located in the approximate center of board 12. Cement 22 consists of a cured mix of Portland cement, silica sand and a plasticizer. The plasticizer permits the board to retain a limited amount of flexibility. Many suitable plasticizers are available for use in the construction of board 12 including Plastifier Bu-40™ from Sika™. (or any plasticizer equivalent thereto). In the case of Plastifier Bu-40, a good finished product having suitable flexibility is created by adding sufficient plasticizer to equal approximately 2% of the weight of the cement. In addition, up to about 0.5% by weight of a water resistance additive such as Plastocrete DM™ from Sika™ (or any water resistance additive equivalent thereto) may be added to increase the water resistance of the finished product.

Fabric mesh screen 18 is embedded into surface 16 and acts to keep the surface contiguous and free from cracking and crumbling. In order to ensure that the fabric screen acts to keep surface 16 contiguous, screen 18 is embedded into the cement and is integral thereto. Fabric screen 18 may comprise a polymer fabric screen having a mesh size sufficient to keep surface 16 from crumbling. Alternatively, a fabric screen 18 may consist of a loose fiber mat which is embedded in the surface.

Referring now to FIGS. 3 and 4, the method of manufacturing the scratch board will now be discussed. Firstly, a rectangular form 26 is placed on platform 24. Rectangular form has sides 25, bottom 27 and open top 28. Mesh screen 29 is then placed in form 26. Mesh screen 29 is dimensioned and configured to fit flat in form 26 and completely cover bottom 27. After mesh screen is placed in the form, metal screen 30 is placed in the form. Metal screen 30 is dimensioned to fit flat in form 26 over top of mesh screen 20 and completely cover bottom 27.

After mesh screen 29 and metal screen 30 are placed in form 26, the form is passed under cement hopper/dispenser 32. Hopper 32 is filled with wet cement 35 and has a spout 34 which is configured to permit a continuous ribbon of wet cement 36 to pass through the spout. The composition of cement 35 is selected to ensure that it is capable of flowing freely through spout 34. Form 26 is passed under and through cement ribbon stream 36 at a rate selected to ensure that the form is completely filled as it passes through the stream. Cement ribbon stream 36 is preferably dimensioned to be as wide as form 26 to ensure that the form can be completely filled with wet cement after passing only once through the stream. Vibrator device 40 is positioned on platform 24 and oriented relative to hopper 32 such that form 26 is vibrated while it is being filled with wet cement. Vibrating form 26 permits the wet cement to fill the form more completely without forming air bubbles or air pockets.

After form 26 has been filled with wet cement, level member 38 is passed over the cement form to level the top surface of the wet cement. The cement filled form is then left to cure for at least 24 hours to 7 days. The cured cement board may then be removed from the form and allowed to cure further at room temperature. Depending on the temperature and the relative humidity, the boards will be fully cured within approximately 28 days.

Referring now to FIGS. 5 and 6, the method of using the scratch board of the present invention to construct a tiled floor will now be discussed. Firstly, surface 42 of sub-floor 40 is prepared by sweeping away any large debris which may be present on the sub-floor. Surface 42 does not have to be thoroughly clean or dust free. Boards 12 are then laid on top of sub-floor 40 in abutting end to end fashion. Boards 12 should be laid on the sub-floor with surface 14 facing upwardly. The boards are then secured to the sub-floor by a plurality of metal staples 46. Metal staples 46 consist of a standard U shaped metal staple having a pair of tines 45 and a cross member 44. Board 12 is made sufficiently flexible by the addition of a plasticizer to permit tines 45 to penetrate through the board without cracking the board. Metal screen 20 in board 12 provides the structural support need to prevent cross member 44 from penetrating completely through the board. If metal screen 20 was not present in the board, or if a plastic or fabric screen was used in place of metal screen 20, then staple 46 would be able to pass directly through board 12 and the board could not be securely mounted to sub-floor 40. Staples 46 are applied using a standard staple gun. After boards 12 are stapled to sub-floor 40, an adhesive layer 48 is laid directly onto surface 14 of the boards and then tiles 50 are positioned onto the adhesive layer.

It will be appreciated that covering the sub-floor with boards 12 is a relatively simple and quick procedure. It is simple to install the boards since the workers can walk on top of the boards to install them and secure them to the sub-floor. Furthermore, as soon as the boards are installed on the sub-floor, the process of adhering the tiles to the boards can begin. Finally, since surface 14 of boards 12 is quite flat, the installation of the tiles proceeds quicker since there are fewer bumps and ridges to contend with. The finished floor is also superior since the boards are not bonded to the sub-floor but are attached to it by a plurality of staples. Since boards 12 have a certain degree of flexibility, the boards tend to float over sub-floor 40, providing a smoother and more level finished tiled floor.

A specific embodiment of the present invention has been disclosed; however, several variations of the disclosed embodiment could be envisioned as within the scope of this invention. It is to be understood that the present invention is not limited to the embodiments described above, but encompasses any and all embodiments within the scope of the following claims. 

Therefore, what is claimed is:
 1. A board for laying on a sub-floor to form a foundation for floor tiles, the board comprising: a a rectangular flat board made of cement and having opposite first and second surfaces, b the board having a metal screen extending throughout the board parallel between the first and second surfaces, and c a mesh screen extending throughout the board and positioned adjacent the first surface.
 2. The board of claim 1 wherein the cement is made from a cured mixture of water, silica sand, portland cement and a plasticizer.
 3. The board of claim 1 wherein the cement is made from a cured mixture of water, silica sand, portland cement, a plasticizer and a water repelling agent.
 4. The board of claim 2 wherein the plasticizer is equivalent to Plastifier Bu-40.
 5. The boar of claim 3 wherein the water repelling agent is equivalent to Plastocrete DM™.
 6. A method of manufacturing a tile floor using the boards of claim 1 comprising the steps of a covering the sub-floor with a plurality of boards and securing the boards to the sub-floor with a plurality of staples, b spreading a tile adhesive overtop of the boards after the boards have been secured to the sub-floor and then c laying the tiles onto the adhesive.
 7. A method of manufacturing the board of claim 1 comprising the steps of a placing the mesh screen into a rectangular form, b placing the screen over top of the mesh screen in the rectangular form, c pouring wet cement into the rectangular form containing the mesh screen and metal screen, d leveling the cement to form one of the surfaces and e curing the cement before removing the finished board from the form. 